Extremely complicated.
A taste:
The implications of the tribal revolt have been somewhat overlooked by the news media and in the public debate in Coalition capitals. In fact, the uprising represents very significant political progress toward reconciliation at the grass-roots level, and major security progress in marginalizing extremists and reducing civilian deaths. It also does much to redress the lack of coalition forces that has hampered previous counterinsurgency approaches, by throwing tens of thousands of local allies into the balance, on our side. For these reasons, the tribal revolt is arguably the most significant change in the Iraqi operating environment for several years. But because it occurred in ways that were neither expected nor accounted for in our “benchmarks” (which were formulated before the uprising began to really develop, and which tend to focus on national legislative developments at the central government and political party level rather than grass-roots changes in the quality of life of ordinary Iraqis) the significance of this development has been overlooked to some extent.
One obvious outcome of the uprising is the political band-wagoning effect we are currently seeing: tribal leaders see the benefits other tribes have gained from turning against terrorists, and want the same benefits themselves, so they too turn against extremists in their own areas. At the same time, the Government of Iraq sees benefits in terms of grass-roots political reconciliation and reduced violence, and is keen to take control of, and credit for, the process. Provincial governments also see the benefits of self-securing districts, freeing up police and military forces for other tasks. This has the potential to help coalesce Iraqi society around competent, non-sectarian institutions (albeit informal ones).
h/t Conservative Grapevine